Uwe Dippel wrote: > [i]google found that solaris does have file change notification: > http://blogs.sun.com/praks/entry/file_events_notification > [/i] > > Didn't see that one, thanks. > > [i]Would that do the job?[/i] > > It is not supposed to do a job, thanks :), it is for a presentation at a > conference I will be giving. I was wondering if Solaris offered CDP, > Continuous Data Protection, like > http://en.wikipedia.org/wiki/Continuous_data_protection > To me, "Continuous data protection is different from traditional backup in > that you don't have to specify the point in time to which you would like to > recover until you are ready to perform a restore. Traditional backups can > only restore data to the point at which the backup was taken. With continuous > data protection, there are no backup schedules" is a perfect match to the > revolutionary design of ZFS; and I am sure the next TimeMachine of Apple will > have it. > File change notification as system call is not the optimum, probably. The > overhead could be pretty high in comparison with the file system (ZFS) itself > noticing a change, a 'write', and on own initiative storing the block to be > replaced in a 'back-in-time'-queue. > > TimeMachine is limited, as it allows to roll to specified moments in time > only. Multiple changes in between those snapshots will be lost. > A StateMachine will allow to roll to any specific state, to each state a file > ever had had. > Think log files of a RDBMS, without the overhead. > > Uwe > ZFS can't currently provide continuous data protection. Even if you triggered snapshots with every file change, on a large or busy file system, the snapshots would not be able to keep up and you would quickly overload your system. Snapshots are light weight, but not resource free. It's the wrong way to time stamp your data. Too global.
I think this would be a very worthwhile project for the ZFS team to take on. CDP could be easily implemented by simply marking every block write once, and then a policy could be put in place to expire old blocks as a user defined parameter. This would ensure free space remains in the file system. Then AVS could be deployed for remote replication and bingo. Maybe I'm missing something but this seems like a no brainer. Train of thought here, but you could do better than most CDP offerings, in that you could not only offer to recover the file system from an instant in time, but you could selectively recover a single file from an instant in time. That would be killer. In some circles, CDP is big business. It would be a great ZFS offering. Jon _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
